Lap dissolve slide projector

ABSTRACT

A lap dissolve slide projector alternately displays slides supported in two laterally adjacent stationary slide gates provided with corresponding separate objective lens systems. A single multiple compartment slide tray moves laterally into alternate alignment with one gate and then the other, and also advances and retracts automatically so that the slides are fed into the projector and displayed in the sequence in which they are initially arranged in the tray and are returned to the tray in the same sequence.

United States Patent Harvey Sept. 5, 1972 [54] LA? DISSOLVE SLIDEPROJECTOR k 3,501,231 3/19'10 Fisher ..353/82 Inventor: Donald M. HarveyRochester Jackson NY. 14650 Primary Examiner-Leonard Forman 73 A 2 EAssistant Examiner-Steven L. Stephan Sslgnee gi g YKodak Company RochAttorney-Robert W. Hampton and Steve W.

9 b 22 Filed: May 14,1970 Grem 21 Appl. No.: 37,227 ABSTRACT A lapdissolve slide projector alternately displays 52 US. Cl. ..353/90,353/83, 353/94, slides upp in o laterally adjacent stationary 353 103slide gates provided with corresponding separate 0b- 51 161. Cl....G03b21/14, G03b 21/26, G03b 23/02 J lens system A single t p q p q 58 Fieldof Search ..353/82, 83, 86, 93, 90,94, shde y moves laterally Intoalternate allgnmem Wlth 353 103 4 49 105 10 109 one gate and then theother, and also advances and v retracts automaticallyso that the slidesare fed into 5 R f n Cited the projector and displayed in the sequencein which they are initially arranged in the tray and are returned UNITEDSTATES PATENTS 'to the tray in the same sequence. 3,264,937 8/1966 Antos..3s'3/s3 10 Claims 26 0mm Figures 3,468,603 9/1969 Kovarik et a1...353/90 PATENTED 5'97? I 3.689.140

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'DONALD M. HARVEY INVENTOR. BYfliK/M I fiMK M ATTORNEYSP'A'IE'N'T'E'DSEP 5 I972 CAM ROTATION LOCKING PAWL INDEXING PAWL SLIDELIFTER GATES CARRIAGE BI SLIDE TRAY cAM ROTA ION ENGAGED FREE ENGAGEDFREE C.C.W.

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Z 'fAm/M ATTORNEYS LAP DISSOLVE SLIDE PROJECTOR BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates to lapdissolve slide projectors which alternately display slides supported inside by side relation to each other in two laterally adjacent gatesprovided with respective separate lens systems, whereby one projectedimage gradually fades and disappears as the next projected imagesimultaneously comes into view. More particularly, the present inventionenables such a projector to be loaded with a single slide tray in whichthe slides are initially arranged in chronological display sequence andto which the slides are returned automatically in that same sequenceafter they have been displayed.

2. Description of the Prior Art The pleasing effect of lap dissolveslide projection has long been recognized and has given rise to numerousattempts to develop commercially acceptable projectors of that type.Basically, such a projector generally includes two laterally adjacentstationary slide gates, each of which is associated with its ownobjective lens system, whereby an image of a slide in either gate can beprojected at the same location on a projection screen. As the slide inone gate is being displayed, the previously projected slide is removedfrom the other gate and replaced by the next slide to be shown. Tochange from one projected image to the next, the brightness of the imagebeing displayed is gradually reduced while the projected image of theslide in the other gate is gradually increased in brightness, thuscausing the former image to fade away as the latter image simultaneouslycomes into view.

In most previously known lap dissolve projectors of the type describedabove, the fact that successive slides must be located alternately intwo separate slide gates has necessitated the use of two slide trays,each of which provides slides only to the corresponding gate. Since theslides must be arranged in the two trays in uninterrupted alternatesequential order, this approach greatly complicates the task of editingor re-arranging the sequence in which the slides are to be displayed.Furthermore, the alternate sequential arrangement of the slides dictatedby sucha lap dissolve projector makes it impossible to display the sametray of slides in proper sequence with a conventional projector, or viceversa, without first re-arranging all of the slides. Alternatively, lapdissolve slide projectors of the same general type have been proposedwhich deliver successive consecutively arranged slides alternately intotwo slide gates from a single tray, but which do not preserve theoriginal slide sequence, thus requiring the slides to be re-arrangedeach time they are displayed.

SUMMARY OF THE INVENTION The present invention likewise involves slideprojectors embodying two stationary slide gates provided withcorresponding objective lens systems, as described above, but utilizesonly one slide tray in which the slides are arranged in chronologicaldisplay sequence. A tray shifting mechanism incorporated in theprojector moves the tray laterally to align it alternately with one gateand then the other and also advances and retracts the tray automaticallyso that the slides are fed into the projector and displayed in the samesequence in which they are originally arranged and are then returned tothe tray in that same sequence. Although the invention can be adapted toother types of slide trays, the illustrative preferred embodimentemploys rotary gravity feed trays of the popular type disclosed in U.S.Pat. No. 3,276,314, issued to the assignee of the present invention on 4Oct. 1966, which are fully compatible with either the subject projectoror with existing projectors, without requiring re-arr'angement of theslide sequence.

In addition to providing the basic means-for accomplishing theabove-described mode of projector operation, the present invention alsoembodies many other advantageous features which are equally applicableto conventional tray loaded slide projectors to improve operationalconvenience and reliability and to minimize wear or accidental damage tothe slides. Moreover, the subject projector also embodies simple andreliable means for allowing the slides to be shown in reverse order orin any other selected sequence and for providing remote controloperation.

Various means for practicing the invention and other advantages andnovel features thereof will be apparent from the following detaileddescription of the illustrative preferred embodiment of the invention,reference being made to the accompanying drawings in which likereference characters denote like elements.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of a lap dissolve projector comprising anillustrative preferred embodiment of the present invention;

FIG. 2 is a fragmentary partically cross sectioned front elevationalview of the projector shown in FIG. 1;

FIG. 3 is a top plan view of the slide tray used with the subjectprojector;

FIG. 4 is a bottom view of the slide tray shown in FIG. 3;

FIG. 5 is a plan view of the projector with the slide tray removed,illustrating in broken lines the two positions of the slide tray and thelocations of the internal elements of the projectors optical system;

FIG. 6 is a somewhat diagrammatic perspective rear view of the opticalelements of the projector;

FIG. 7 is a plan view of the projector partially broken away to depictthe drive motor, the tray positioning carriage and the cam means bywhich the carriage is moved to its two operative positions;

FIG. 8 is a fragmentary partially cross sectioned left side elevationalview of the projector of FIG. 7 illustrating the mechanism incorporatedin the tray positioning carriage, other mechanisms of the projectorbeing omitted for purposes of clarity;

FIG. 9 is a bottom view of the cam assembly embodied in the traypositioning carriage;

FIG. 10 is an exploded perspective view of the elements, some of whichare broken away, comprising the tray indexing mechanism of theprojector;

FIG. 11 is a front elevational view of a portion of the elements of FIG.10 showing the cam follower tongue member which actuates the pawlengaging and releasing slide of the mechanism shown in FIG. 10 and whichis movable to two positions to permit the projector to display slides ineither forward or reverse sequence;

FIG. 12 is a plan view of the cam follower tongue member shown in FIG.11;

FIG. 13 is a plan view of the slide tray indexing mechanism comprisingthe various elements depicted in FIG. 10, showing the respectivepositions assumed by those elements while a slide is being projected;

FIG. 14 is a view similar to FIG. 13 showing the slide indexing elementsin the respective positions which they assume as the tray is beingindexed in a counterclockwise direction during a slide changingoperation;

FIG. 15 is a perspective rear view of the slide gate structure embodiedin the projector;

FIG. 16 is a side elevational view of the slide gate structure shown inFIG. 15;

FIG. 17 is a fragmentary, partially cross sectioned rear 'elevationalview of the projector showing the operative elements of the slidetransfer and gate opening mechanisms therein; FIG. 18 is a fragmentary,partially cross sectioned plan view of the gate opening, slide transferand select release mechanisms of the projector, showing the illustratedelements of those mechanisms in the respective positions which theynormally assume between slide changing operations;

FIG. 19 corresponds to FIG. 18 and depicts the respective positions ofthe illustrated projector elements during a slide changing operation orwhile the select-release mechanism is performing its intended function;

FIGS. 20 through 22 are schematic plan views illustrating alternate pawland tray lug configurations adapted to prevent accidental misalignmentbetween the lugs and pawls;

FIG. 23 is a perspective view of the lens focusing system of theprojector; v

FIG. 24 is a schematic wiring diagram of the projector;

FIG. 25 is a chart showing the timed relation between the functions ofthe various elements of the projector during two consecutive slidechanging cycles performed in the projectors forward mode of operation;and

FIG. 26 corresponds to FIG. 25 but shows the timed sequence in which thedepicted functions occur when the projector is in its reverse orselect-release mode of operation.

DESCRIPTION OF THE ILLUSTRATIVE PREFERRED EMBODIMENT To summarize theillustrated preferred embodiment of the present invention, withoutregard to specific structural and operational features hereinafterexplained in detail, reference is first made to FIGS. 1-5. From thosefigures, it is apparent that the projector comprises a generallyrectilinear housing 11 provided with an opening 12 in its front wallmember 13 to accommodate two laterally adjacent generally parallel leftand right objective lens assemblies 14 and 15. To simplify explanationsof the construction and'mode of operation of the projector, the termsright and left are used herein with reference to viewing the projectorfrom the front and alternate right and left positions of variousprojector elements are indicated by the respective suffixes R or Lfollowing the corresponding reference character. Similarly, unlessotherwise indicated, reference to clockwise or counterclockwise rotationof various elements of the projector mechanism will be understood torefer to a top view of such elements.

A multiple compartment rotary slide tray 16, corresponding generally tothe one disclosedin the previously-identified Robinson patent, isremovably mounted in a horizontal position on a cylindrical spindle 17,which projects upwardly through an elongate slot 18 in the flat top wallmember 19 of housing 11. Spindle 17 is movable laterally to the twopositions shown at 17L and 17R in FIG. 5, thereby effecting lateralmovement of the slide tray to the corresponding positions shown at 16Land 16R in the same figure.

A slide gate structure 21 is located within housing 1 1 below opening 22in the top wall member thereof and comprises two laterally adjacent leftand right slide gates 23 and 24 aligned respectively with lensassemblies 14 and 15. When the slide tray is in its left position, oneof the tray compartments 25 (see FIG. 1) is aligned with index pointer26 and is located directly above left slide gate 23 sothat a slide 27 inthat compartment can be fed downwardly into that gate through opening 22in housing 1 1. Similarly, when the slide tray is in its right position,the slide in the tray compartment aligned with pointer 26 can be loadedinto gate 24.

The slides 27 are arranged in chronological display sequence in aclockwise .direction in the slide tray, which is rotationally indexed byan indexing mechanism in the projector to position the tray compartmentsin vertical alignment with the film gates in coordinated relation withthe lateral movement of the slide tray. While a slide is being projectedin one of the film gates, the slide tray is positioned with the nextslide located directly above the other gate, which is then empty andobscured from the corresponding projection lens system by a movable maskmember. To display the next slide, the operator momentarily pushes theforwar button 28 on remote control unit 29, which causes that slide todrop by gravity into a projection position in the empty gate. When thishas been accomplished, the slide tray shifts automatically into itsother lateral position. During this lateral movement of the slide tray,the mask member moves in unison therewith to gradually uncover the slidethat was just loaded into the gate and simultaneously to graduallyobscure the preceding slide; whereby the projected image of the formerslide comes into view with increasing intensity while the image of thelatter slide fades away.

When the slide tray has completed its lateral movement into alignmentwith the gate containing the previ ously displayed slide, the tray isrotationally retracted in a clockwise direction by one compartmentincrement to allow that slide to be raised into the tray compartment inwhich it was originally housed. Thereupon, the' tray is advancedautomatically in a counterclockwise direction by two compartmentincrements to locate the next slide in the display sequence directlyabove the now empty gate, thus completing a slide changing cycle. Inresponse to the next actuation of the forward button, the same sequenceof operations is repeated in coordination with the lateral movement ofthe tray in the opposite direction, thereby restoring the mechanism toits former condition. Consequently, each successive depression of theforward button causes the next slide to come into view on the screen asthe preceding one fades out of view and is then returned to its originaltray compartment. By depressing the reverse button 31 on the remotecontrol unit, the operator can cause the mechanism to perform in thesame general manner but with a different tray indexing sequence so thatthe previously displayed slide can be viewed again.

Because of the means employed to retain all of the slides in the slidetray when the tray is removed from the projector, the tray must berotated to a predetermined loading position before it can be installedon or removed from the projector. During the operation of the projectordescribed above, one slide is always located in a projection gate andthe slide tray is at all times engaged by the tray indexing mechanismwhich controls its rotational indexing movement. Therefore, if theoperator wishes to remove the tray without having displayed all of theslides or to skip one or more slides in the projection sequence, it isnecessary first to raise the slide in the'projector back into its propertray compartment and then to disengage the indexing mechanism from thetray. so that the latter can be rotated manually to the desired positionwhile both gates remain empty. Accordingly, the projector is alsoprovided with a mechanism which automatically performs those operationsin response to manual depression of a select-release button 32 on theprojector housing.

Since successive slides are projected alternately from one gate and thenthe other through the corresponding separate objective lens systems,focusing of the image being projected requires axial movement of thecorresponding lens system but should not disturb the other lens system.Therefore, focusing switch bar 33 on the remote control unit 29 isautomatically connected electrically with the focusing mechanism of theparticular lens system then in use to allow that lens system to beadjusted forwardly or rearwardly by rocking the switch bar one way orthe other, without disturbing the adjustment of the other lens system.

SLIDE TRAY AND TRAY SPINDLE As best shown in FIGS. 2, 3 and 4, the slidetray 16 comprises a cylindrical plastic tray member 34 includingconcentric inner and outer shells 35 and 36 connected by a plurality ofradial separators 37 to provide a corresponding plurality of equallyspaced radially disposed slide compartments 25. In the illustratedembodiment, there are 81 separators and slide compartments in the traymember, but only a few of the separators and compartments are shown inFIG. 3 in order to simplify that figure. A peripheral rim 38 projectingoutwardly from the lower edge of outer shell 36 is provided withreference numerals shown at 39, which correspond to and designate therespective slide compartments. Tray indexing lugs or pins 41 projectdownwardly from rim 38, each of such lugs likewise being inpredetermined aligned relation to a corresponding one of the slidecompartments. With the exception of the compartment aligned with the 0"reference numeral, which is provided with a top closure bridge 42, eachof the slide compartments is adapted to receive slides from either itstop or bottom-end. As shown at numeral 43 in FIG. 2, each separator 37ineludes an arcuate notch in its upper edge to facilitate manuallyinstalling and removing slides from the slide compartments.

An annular lip 45 projects inwardly from the inner tray shell 35 anddefines a central circular hole 46 adapted to receive the cylindricaltray spindle 17 of the projector. As later described in connection withthe detailed explanation of the select-release mechanism illustrated inFIGS. 18 and 19, a locking tongue 47 is slidably mounted in the trayspindle l7 and is retracted to the position illustrated in that figureduring tray loading and unloading operations so that only the narrow tip48 of the tongue projects beyond the periphery of the spindle. Notch 49at the edge of central hole 46 in the slide tray is only of sufficientsize to accommodate the narrow tip 48 of the locking tongue 47 and islocated such that the slide tray 16 can be installed on or removed fromthe projector only when it is oriented with the 0 slide compartmentpositioned over one of the slide gates, i.e. only when the numeral 0 isaligned with index pointer 26. After the tray is installed on theprojector, the locking tongue 47 is located above annular lip 45 and isextended automatically to the position shown in FIG. 5 to prevent tray16 from being removed until the tray member 34 has been returned to itsoriginal loading position and the tongue has been retracted by theselect-release mechanism.

The circular inner and outer edges of an annular metal disc 51 arereceived in shallow recesses in the tray member 34 which definesconcentric inner and outer shoulders 52 and 53. The heads of fourequally spaced screws 54 overlap the circular inner edge of disc 51 toretain the disc in position while allowing it to rotate on shoulder 52.A metal latch plate 55 is located within inner shell 35 of the traymember and is supported above annular lip 45 thereof by molded supportbosses 56 and by its spring fingers 57, which rest on the top surface oflip 45 and bear laterally against the inner shell. Tongues 58 and 59project downwardly from the latch plate through respective openings 61and 62 in tray member lip 45 and are bent over below' that lip tomaintain latch plate 55 in place while allowing it to slide back andforth in the direction of the tongues 58, 59.

An arcuate opening 63 in metal disc 51 includes a pair of opposednotches 64, shown in FIG. 4, through which a slide can pass into and outof the slide compartment aligned therewith. Whenever the slide tray isremoved from the projector, notches 64 are located directly below theunused 0 compartment so that the other slides in the tray cannot fallout of the lower ends of their respective compartments. A cap member 65is removably installed on the tray in engagement with detent bosses 66on the inner wall of shell 35 and includes a rim 67 which overlaps theupper edges of the slides 27 in the tray, thus likewise preventing theslides from falling out of the upper ends of the tray compartments 25 iftray 16 is inverted. To prevent disc 51 from rotating accidentally to aposition at which notches 64 are aligned with a loaded tray compartmentwhile the tray is removed from the projector, tongue 58 of latch plate55 includes a pair of depending ears 68 engageable with mating slots 69in the disc member 51. As long as tray 16 is removed from the projector,spring fingers 57 retain the latch plate 55 in the position shown inFIGS.

3 and 4, which is defined by.the abutment of the inner ends of thespring fingers 57 against support bosses 56. Accordingly, the circularcentral hold 71 in the latch plate is offset slightly from the similarhole 46 in the traybody member 34 and ears 68 of latch tongue 58 remainin rotation blocking engagement with disc 51.

During the installation or-loading of the slide tray onto the projector,tongue 47 initially aligns the slide compartment with index pointer 26and also. aligns positioning hole 72 in metal disc 51 withpositioningpin, 73 (see FIG. 2), which projects upwardly through a slot74 in the top wall of the projector housing as best seeni FIG. 5, andwhich moves laterally along that slot in unison with the lateralmovement of tray spindle 17. As tray 16 is pressed downwardly to itsloaded position, the beveled upper end 75 of spindle 17 enters hole 71in latch plate 55 and cams the plate away from the0 tray compartment towithdraw tongue ears 68 from slots 69 in disc 51 as positioning pin 73simultaneously enters disc positioning hole 72. Consequently, the trayindexing mechanism cannow rotate tray member 34 relative to disc 51,which is positioned with notches 64 of opening 63 in vertical alignmentwithone or the other of the slide gates. Since the 0 compartment of theslide tray-member 34 must be located directly above a slide gate beforetray 16 can normally be removed from the projector, tongue ears 68re-engage slot 69 as such alignment of 0 compartment and slide gateoccurs, thereby again locking the disc so that notches 64 are retainedin alignment with the 0 slide compartment.

MECHANISM CARRIAGE A mechanism carriage, designated generally by numeral76, is located within the projector housing and is best illustrated inFIGS. 7 and 8 of the accompanying drawings. The carriage comprises a topplate 77 which carries spindle 17 and positioning pin 73 (see FIG. andwhich is slidably supported against the top wall member 19 of theprojector housing by gib member 78. A bottom plate 79 is rigidlysupported below and in parallel relation to top plate 77 by front andrear wall members 81 and 82 and thus is movable with the top plate as aunit as the carriage slides to the right or left to effect correspondinglateral movement of the slide tray.

CAMSI-IAFT ASSEMBLY AND DRIVE MECHANISM A vertical camshaft 83 isrotatably supported by the top and bottom plates 77 and 79 of thecarriage and is provided with an upper cam member 84, an intermediatecam member 85 and a lower cam member 86.

The three cam members are connected in fixed relation to each other by apair of screws 87, thereby providing a unitary cam assembly which isrotatable relative to the camshaft.

Below bottom carriage plate 79, a spur gear 88 is pinned to the camshaftand is meshed with a smaller spur gear 89, which is freely rotatable onits support stud 91 and provided with an integral pulley 92. A belt 93connects pulley 92 with the smaller sheave 94 of a double sheave pulley95, which is likewise freely rotatable on camshaft 83. The larger sheave96 of pulley 95, in turn, is connected by belt 97 to armature shaft 98of drive motor 99. Thus, the camshaft 83 is driven continuously in acounterclockwise direction by motor 99 but revolves much slower than themotor shaft and with much more torque.

A flat circular torque limiting clutch vdisc 101 is received in acorresponding recess 102 in the lower cam member 86 as shown in FIGS. 8and 9 and is provided with a spring loaded detent plunger 103 adapted toengage a notch 104 in the edge of recess 102. Accordingly, the camassembly canbe driven by discz101 but the amount of torque that can betransmitted is limited by the force required to cam plunger 103 out ofengagement with notch 104; thereby preventing slide or projector damagewhich might otherwise occur if rotation of the cam assembly wereaccidentally blocked as a result of a malfunction of the machine.

A clutch collar 105 is pinned to camshaft 83 and is provided with aplurality of peripheral teeth 106 adjacent the lower surface of disc101. As previously mentioned, the camshaft rotates continuously in acounterclockwise direction as viewed from the top and therefore drivesthe affixed clutch collar in the same direction, i.e. in a clockwisedirection as viewed from the bottom in FIG. 9.

To perform each slide changing operation, the cam assembly must berotated through a single complete revolution. ACcordingly, the drivemechanism includes a single revolution clutch comprising a dog member107,which is pivotally supported to disc 101 by pin 108 and biased byhairpin spring 109 to urge dog tooth 110 toward engagement with theperipheral teeth 106 of the clutch collar 105. A clutch operating lever111 is pivotally supported to rear wall member 82 of the carriage by apin 112 and is biased upwardly by a leaf spring 113 to the raisedposition depicted in FIG. 8. In that position, lip 114 projectingupwardly from lever 111 is located in the circular path of movement oflip l 15 at the end of the dog member 107 substantially opposite tooth110. Therefore, lip 114 engages lip 115 and holds the dog tooth 110 outof engagement with clutch collar 105 as .a result of the slight torquefrictionally imparted to the cam assembly by camshaft 83 and clutchcollar 105; thus allowing the cam assembly to remain stationary as thecamshaft rotates.

Vertical operating rod 116 extends upwardly through a hole in the bottomcarriage plate 79 and is pivotally connected at its lower end to a bellcrank member 1 17, which is pivoted to a depending flange on the bottomplate of the carriage by pin 118 and connected by link rod 119 to thearmature 120 of a solenoid 121 mounted tothe carriage. A light coilspring 122 encircling the solenoid armature urges the armature towardthe bell crank member 117 and thereby resiliently maintains the verticaloperating rod 116 in its depicted raised position. The bifurcated upperend of rod 116 is pivotally attached to control arm 123 by pin 124extending through opposed elongate rod slots 125. The control am 123, inturn, is pivotally mounted to an extension on the plate 77 of thecarriage by pivot pin 126. A coil spring 127 connects the control armwith rod 116 and resiliently maintains pin 124 in contact with the lowerends of slots 125 as shown in FIG. 8. When the operator energizes thesolenoid by depressing either button 28 or 31 on the remote controlunit, the resulting retraction of the solenoid armature 120 causes thevertical operating rod 116 to move downwardly. When this occurs, clutchoperating pin 128 projecting horizontally from the operating roddepresses clutch operating lever 1 l 1 and disengages its lip 114 fromthe dog member 115, which then moves into engagement with the clutchcollar 105 to couple the cam assembly directly to the camshaft 83. Ifthe solenoid 121 is energized only momentarily to effect each camchanging operation, clutch operating lever 1 11 will have returned toits raised position by the time the cam assembly completes a singlerevolution and will therefore again engage dog member 107 to release thedog tooth 110 from the clutch collar 105, thereby arresting rotation ofthe cam assembly at its initial position. If a malfunction should occurwhich causes disc 101 to slip relative to the cam assembly bydisengagement of the detent 103,104, the initial relation of the disc tothe cam assembly will be restored during the subsequent slide changingoperation after the cause of the malfunction has been corrected.

CARRIAGE SHIFTING MECHANISM As previously mentioned, each slide changingoperation involves moving the slide tray laterally to its oppositeposition in order that successive slides can be projected from alternateslide gates. Since the slide tray is located relative to the projectorby means of spindle 17 carried by the mechanism carriage, the entirecarriage is therefore shifted alternately to the left and then to theright in response to successive complete revolutions of the camassembly. To perform this function, the top face 129 of the upper cammember 84 is provided with a continuous cam slot 130, depicted in FIG.7, which crosses itself as shown at numeral 131 to provide an arcuateouter cam track 132 and an arcuate inner cam track 132 and an arcuateinner cam track 133. A boat shaped cam follower 134 is received in camslot 130 and is pivotally supported by a support stud 135, which isrigidly secured to the top vwall member 19 of the projector housing andextends freely through an elongate slot 136 in top plate 77 of thecarriage. When the cam assembly is positioned as shown in FIG. 7,between slide changing operations, the cam follower member is located atthe midpoint of the inner cam track 133 which is substantiallydiametrically opposed from point 131, and therefore maintains thecarriage 76 at its left position to locate the slide tray in thecorresponding position shown at 16L in FIGS. 1, 2 and 5. During the nextcomplete counterclockwise revolution of the cam member 84, cam follower134 pivots about stud 135 as it follows the profile of the cam slot 130and passes through the slot crossing 131. Since the cam follower supportstud 135 cannot move relative to the projector housing 19, the rotationof the cam assembly causes the entire carriage 76 to shift to the right.When the cam assembly has completed a single revolution, follower 134is'therefore located at the midpoint of the outer cam track 132 which issubstantially diametrically opposed from point 131, and thus locates theslide tray in its right position as shown at 16R in FIG. 5. Hence, byalternately following the inner and outer cam tracks 133,132respectively, the cam follower 134 causes the slide tray 16 to beshifted laterally to its opposite position during each slide changingoperation. As the carriage 76 moves between its two alternate positions,the distance between shaft 98 of motor 99 and pulley sheave 96 obviouslychanges somewhat, but by locating the motor with its shaft behind theintermediate position of the camshaft, as shown in FIG. 7, this distancevariation can be readily accommodated by stretching of the resilientdrive belt 97.

TRAY INDEXING MECHANISM The tray indexing mechanism, shown in detail inFIGS. 10 through 14, includes a tray indexing pawl 137 and a traylocating pawl 138, which are adapted to engage theslide tray member 34by entering between two adjacent indexing lugs 41 thereof. The trayindexing pawl 137 projects upwardly from a pawl plate139, which issupported by top plate 77 of carriage 76 above opening 141 in thatplate. Below top plate 77 of the carriage, indexing lever 142 ispivotally supported thereto by a pivot stud 143. A tongue 144 on theindexing lever is provided with a cam follower pin 145 received inendless cam slot 146 in the u-per face of intermediate cam member 85,whereby rotation of the cam assembly affects angular movement of theindexing lever 142 between its extreme counterclockwise and clockwisepositions shown respectively in FIGS. 13 and 14. Pawl engaging slide 147is slidably supported immediately below indexing lever 142 by means ofstuds 148 projecting downwardly from the top plate 77 of the carriage 76through elongate slide slots 149. A cam follower tongue 151, describedin detail below, is movably supported at the end of the slide plate 147adjacent intermediate cam member 85 and is maintained adjacent one ofthe two peripheral cam surfaces 152 and 153 of cam member 85 by spring154. As the cam assembly rotates, the slide plate 147 is therefore movedlaterally between its right and left positions shown respectively inFIGS. 13 and 14.

Pawl plate 139 includes a guide lug 155 projecting downwardly therefromthrough opening 141 in the top plate 77 of the carriage, throughelongate slot 156 in indexing lever 142 and through arcuate slot 157 inpawl engaging slide 147. A large headed screw 158 is threaded into thelower end of lug 155 and overlaps the edges of arcutat slot 157, therebypreventing pawl plate 139 from moving upwardly. Thus, the position ofthe tray indexing pawl 137 is established by elongate slot 156, which islocated in generally radial relation to the circular row of slide trayindexing lugs 41 and controls latent movement of pawl 137, and byelongate slot 157, which is substantially concentric with the row ofindexing lugs and controls radial movement of pawl 137.

Tray locating pawl 138 projects upwardly from the right free end of pawlarm 159 which is pivotally attached to the top plate 77 of the carriagein horizontal alignment with pawl engaging slide 147 by stud 161. Aspring 162 biases the pawl arm 159 in a clockwise direction to maintainit in resilient engagement with the adjacent curved end surface 163 ofthe pawl engaging slide 147. Therefore, when slide 147 is in its rightposition between slide changing operations as seen in FIG. 10, traylocating pawl 138 is received between two adjacent tray indexing lugs 41to prevent the tray member 36 from rotating and tray indexing pawl 137is maintained in an inoperative position beyond engagement with the trayindexing lugs. When the pawl engaging slide 147 moves to the left duringa slide changing operation, as shown in FIG. 14, it displaces pawl arm159 to withdraw the tray locating pawl 138 from the tray indexing lugs41 as the tray indexing pawl 137 is received between two of those lugs.

The upper and lower peripheral cam surfaces 152, 153 respectively ofintermediate cam member 85 are separated by annular flange 164 providedwith a slot 165, which is located in alignment with cam follower tongue151 when the cam assembly is in its initial position shown in FIGS.through 13. By reference to FIGS. 11 and 12, it will be apparent thatthe cam follower tongue 151 includes an ear 166 which fits looselythrough a slot 167 in the vertical portion 168 of pawl engaging slide147. A rivet 169 is secured to the horizontal portion 170 of the pawlengaging slide and extends freely through a hole 171 in ear 166. A lightcoil spring 172 is compressed between ear 166 and the head of rivet 169,thereby biasing the ear against the lower surface of the horizontalportion 170 of slide 147 to resiliently hold the tongue in its raisedposition in alignment with the upper cam surface 152, as shown in FIGS.10 and 11. When the tongue 151 is depressed to its lower'position showninbroken lines in FIG. 11, however, its tip is aligned with the lowercam follower surface 153 below flange 164 of cam member 85. Control arm123 is provided with an elongate tip 173 which is located immediatelyabove tongue 151 and which depresses the tongue" to its lower positionwhenever solenoid 121 is energized.

By reference to the schematic wiring diagram of FIG. 24, it will be seenthat depression of the forward button 28 of remote control unit 29closes a normally open switch 174, which connects the solenoid withpower supply plug 175 through a normally closed momentary contact switch176. The latter switch comprises clutch operating lever 111 and lip 115of dog member 107, which engages conductor strap 177 as shown in FIGS.8, 9, and 24. When the cam assembly is in its initial position, betweenslide changing operations, lip 114 of lever 1 11 is in contact with lip115 of the dog member, which in turn is is contact with conductor strap177. Accordingly, current can flow through the closed switch from lever111 to strap 177. When the operator closes switch 174, the resultingenergization of solenoid 121 engages the cam drive clutch andsimultaneously moves tongue 151 downwardly through flange slot 165 toits lower position. Since lip 114 of the clutch operating lever 111thereupon releases lip 115 of the dog member 107, the latter is movedinstantly into engagement with clutch collar 105 by spring 109, as shownin broken lines in FIG. 9, thus disengaging lip 115 from conductor strap177 to open switch 176. Consequently, solenoid 121 is immediatelyde-energized to allow tongue 151 to return to its raised positionthrough slot 167 before the cam assembly has moved that slot beyond thetongue. Reverse button 31 of the remote control unit is similarlyadapted to close a normally open switch 178, which is connected directlyin series with power supply plug 175 and solenoid 121. When this buttonis depressed, tongue 151 is therefore moved to its lower position in thesame manner just described and the cam assembly simultaneously starts torotate. Since switch 178 remains closed until button 31 is manuallyreleased, the time required for the operator to depress and release thebutton in a normal manner therefore allows the cam rotation to move slot167 beyond tongue 151 before solenoid 121 is de-energized; thus trappingthe tongue below flange 164 in alignment with the lower cam surface 153.If desired, a delayed action relay or the like, not shown, can also beincluded in the reverse operation circuit to insure that even asubstantially instantaneous depression and release of button 31 willcause solenoid 121 to remain energized until flange slot 167 has movedbeyond tongue 151.

FORWARD OPERATION The sequence of operation involved in indexing andshifting the slide tray 16 in response to depression of the forwardbutton 28 can best be understood by referring to FIGS. 13 and 14 inconjunction with FIG. 25, which shows diagrammatically the correlationbetween the timing of various operations performed by the projector inits forward mode of operation.

Whenever the cam assembly is in its initial position, cam follower pin145 of indexing lever 142 is located along the innermost'track segment179 of cam slot 146 in intermediate cam member ,'thereby locating theindexing lever in its extreme counterclockwise position shown in FIG.13. Concurrently, tongue 151 is aligned with the inner arcuate surface180 of the upper cam surface 152 of cam member 85, thereby maintainingthe tray indexing pawl 137 beyond engagement with the tray indexing lugs41 and allowing tray locating pawl 138 to be received between two of thetray lugs 41. As cam member 85 rotates in a counterclockwise direction,cam follower pin moves outwardly relative to the camshaft 83 asit'enters the outermost cam track segment 181 and then returns to anintermediate position as it enters the intermediate cam track segment182. Accordingly, indexing lever 142 moves from its initial extremecounterclockwise position to its extreme clockwise position shown inFIG. 14 and then returns to an intermediate position between the twopositions shown in FIGS. 13 and 14. During such movements of theindexing lever 142, however, the raised tongue 151 of the pawl engagingslide 147 remains in alignment with the inner arcuate surface of cammember 85 so that the tray indexing pawl 137 remains in its inoperativeposition and has no influence on the immoblized slide tray member 34.

While the cam assembly continues to rotate, the upper cam member 84causes the carriage 76 and the slide tray 16 to shift to theirrespective opposite positions. When the shifting of the slide tray iscomplete, cam lobe 183 on the upper cam surface 152 of cam member 85comes into alignment with tongue 151 while indexing lever 142 is stilllocated in its intermediate position. Thereupon, pawl engaging slide 147is moved to the left in opposition to spring 154 to introduce pawl 137between the adjacent pair of tray indexing lugs 41 as pawl 138 issimultaneously disengaged from the tray indexing lugs. The otheroutermost cam track segment 184 of cam slot 146 then moves intoalignment with pin 145 on indexing lever 142, thus causing the latter tomove from its intermediate position to its extreme clockwise position,to dwell there momentarily and then to move back to its extremecounterclockwise position as the cam assembly completes its rotation.Thus, after the slide tray 16 has been shifted, the tray member 34 isretracted in a clockwise direction by one compartment increment, allowedto remain momentarily in that position, ad then advance in acounterclockwise direction by two complartment increments to completethe slide changing cyc e.

In the event the cam assembly were to be accidentally jammed with tongue151 located above flange 164, thereby causing the drive clutch 103, 104to slip solenoid 121 could not effect subsequent depression of clutchoperating lever 111 if vertical operating rod 116 were positivelyconnected to control arm 123. Under these circumstances, however, and byvirtue of elongated slot 125 which permits relative movement between arm123 and rod 1 16, the solenoid 121 is sufficiently powerful to move rod116 downwardly by stretching spring 127, thereby allowing the clutchoperating lever 111 to be released from dog member 106 notwithstandingthe fact that the control arm 123 is blocked against downward movementby cam follower tongue 151.

REVERSE OPERATION When the counterclockwise rotation of the cam assemblyis initiated by depression of reverse button 31, the resulting angularmovement of the indexing lever 142 and the shifting movement of theslide tray 16take place in exactly the same manner and sequencedescribed above but the lateral movement of the pawl engaging slide 147is controlled by the lower cam surface 153 of cam member 85, rather thanby the upper cam surface 152. As shown in FIGS. 13 and 14, lower camsurface 153 is substantially identical in profile to the upper camsurface but is rotationally displaced therefrom so that tongue 151 isengaged with lower cam lobe 185 while the outermost track segment 181 ofcam member 85 is engaged with cam follower pin 145. Therefore, withreference to FIG. 13, the initial rotation of the cam assembly causesthe tray member 34 to be retracted or moved in a counterclockwisedirection by two compartment increments, allowed to dwell in thatposition, and then advanced by one compartment increment and re-engagedby pawl 138 as the inner arcuate cam segment 186 rotates into alignmentwith tongue 151. During the subsequent continuing rotation of the cam'assembly, the tray 36 is shifted and the indexing lever 142 then movesagain as follower pin 145 enters and leaves cam track segment 184 of cammember 85. The latter movements of the indexing lever have no influenceon the tray member, however, due to the fact that the pawl engagingslide 139 remains in its right position and thereby maintains trayindexing pawl 137 out of engagement with tray lugs 41.

SLIDE'GATE STRUCTURE The two slide gates 23 and 24 are provided by theslide gate structure 21, shown in FIGS. and 16, which comprises a frameplate 187 rigidly attached to the base plate 188 of the projectorhousing by screws 189. Above its vertical lower portion 191, the frameplate is bent forwardly and then upwardly to provide a horizontal shelfsection 192 and vertical front wall sections 193, 194 and 195, which areseparated by openings 196 and 197 extending into the shelf section.Rearwardly projecting end wall members 198 and 199 are carriedrespectively by the front wall sections 193 and and are provided withoutwardly sloped upper ears 201 corresponding to the forwardly slopedupper end portions 202 of the front wall sections. A separator bar 203extends upwardly along the back of the central front wall section 194and is spaced from both end wall members by a distance just slightlymore than the width of a slide 27. ACcordingly, a slide located behindeither of the two front wall openings 196 or 197 rests on shelf section192 and is laterally positioned between separator bar 203 and thecorresponding end wall member 198, 199.

To insure that slides in the film gates are maintained in contact withthe corresponding rearward surfaces of the front wall sections and willbe positioned in proper relation to the respective lens systems, twopressure members 204 and 205 are pivotally supported to frame plate 187rearwardly of the corresponding slide positions by hinge pin 206. Eachof the pressure members includes two fingers 207 adapted to engage themarginal rearward faces of a slide 27 received in the correspondingslide gate without obstructing the central slide transparency 208thereof. Light coil springs 209 connecting the lower tongues 21 1 of thepressure plates to stationary ear 212 of frame plate 187 bias fingers207 forwardly into resilient engagement with the corresponding slides.As explained in greater detail below, the nose portion 213 of a gateopening lever 214 supported by carriage 76 is adapted to press forwardlyon tongues 211 in alternate sequence and in timed relation to the slidechanging operations to alternately open the gates by retracting thecorresponding pressure plate fingers 207 as shown at the empty gate 23in FIG. 15 and in broken lines in FIG. 16. When either of the gates isin this open condition, a slide 27 allowed to drop into that gate fromslide tray 16 through housing opening 22 is therefore guided into itsprojection position by the sloped ears 201 and 202 of the frame plate187 and by the rearwardly sloped upper ends 215 of fingers 207 before itis engaged by the fingers to seat it firmly against the correspondingfront wall sections.

' OPTICAL SYSTEM Referring again to FIGS. 5 and 6, the two illustratedslides 27 in gates 23 and 24 are shown in their respective projectionpositions which they assume while supported in the corresponding leftand right slide gates 23 and 24. The previously mentioned objective lensassemblies 14 and 15 are located forwardly of the illustrated slideswith their respective stationary parallel optical axes 216 and 217passing through the centers of the corresponding slide transparencies208 in normal relation thereto. As illustrated in FIG. 23 and describedlater in detail, the objective lens assemblies are adjustableindependently along their respective axes, thereby allowing both lenssystems to focus images of their respective slides within substantiallythe same area on a remote projection screen.

To illuminate simultaneously the transparencies 208 of the slideslocated in both gates, two condenser lens systems 218 and 219 arelocated along the respective optical axes 216 and 217 rearwardly of theslides 27. Mirrors 221 and 222 are mounted diagonally behind therespective condenser lens systems 218 and 219 by appropriate supportmeans and are tilted toward the filament of projection lamp 223 so thateach mirror reflects light from the lamp to the respective condenserlens system, thereby illuminating the corresponding slide transparency.Other types of illumination systems could of course be employed, forexample one utilizing a single horizontal cylindroid condenser lenssystem adapted to provide a single light beam of sufficient width toilluminate both slide transparencies at once.

Closely behind the two objective lens assemblies 14, 15, a mask member224 is carried by the top plate 77 of carriage 76. When the carriage isin its right position, mask member 224 is located in front of slide 27in slide gate 24 and therefore prevents the image of that slide frombeing projected onto the projection screen. As the carriage 76 and slidetray 16 shift to the left during a slide changing operation, mask member224 likewise shifts to the position shown in broken lines in FIG. 6 sothat only the image of slide 27 in slide gate 24 is then visible on thescreen. It should be noted, however, that during the shifting movementof the mask member 224, its V-shaped endv notches 225 gradually uncoverone slide and simultaneously gradually obstruct the other one so thatthe projected image .of the preceding slide 'fades in intensity as theimage of the next slide brightens into view at the same location on thescreen; thus presenting a pleasing uninterrupted transition betweensuccessive images. After each previously displayed slide has beenreplaced in the gate, each subsequent shifting movement of the carriageobviously causes the same lap dissolve effect to be repeated.

SLIDE TRANSFER MECHANISM The mechanism employed to lower slides from theslide tray into the slide gates and to return the slides from the gatesinto the tray is best shown in FIGS. l5

through 19. This mechanism comprises a lifter arm 226 located just aheadof the slide gate structure and rigidly connected to a cross bar 227,which is pivotally supported between the front and rear members of thecarriage by pivot studs 228. A cam follower finger 229 car- ,ried bycross bar 227 is adapted to ride against the periphery of slide loadingcam 231 of the lower cam member 86 as best seen in FIGS. 18 and 19. Whenthe cam assembly is in its initial position, lobe 232 of cam 231 isengaged with cam follower finger 229 and thereby causes the lifter armto assume its raised position shown in solid lines in FIGS. 15 and 17.In this position, lifter pad 233 at the upper end of arm 226 is receivedin arcuate opening 63 in the slide tray disc 51 to support the slidealigned with opposed disc notches 64. Therefore, as long as the lifterarm remains in its raised position, the slide tray 16 can be indexed butnone of the slides 27 can drop out of their respective traycompartments.

As the rotation of the cam assembly moves lobe 232 beyond cam followerfinger 229, arm 226 drops to its lowered position shown in solid linesin FIG. 16 and in broken lines in FIG. 17. Accordingly, as the lifterpad moves downwardly through opening 196 or 197 in the slide gatestructure, the slide aligned with disc notches 64 drops into projectionposition in the corresponding gate, which is temporarily held open asdescribed below. As will be evident from FIGS. 25 and 26, this slideloading operation occurs after the cam assembly has rotated sufficientlyto produce the initial tray indexing movement required during theprojectors reverse mode of operation, but before the tray 16 andcarriage 76 have shifted laterally. By the time the tray shiftingoperation commences, lifter pad 233 is therefore positioned below shelfsection 192 of the gate structure so that the lifter arm 226 can movesideways with the carriage to position the lifter pad below the slidelocated in the opposite projection gate. After the tray shiftingoperation is completed, lobe 232 of cam 231 again moves into alignmentwith cam follower finger 229, thus causing the lifter pad 233 to raisethat slide out of the gate and back into its slide tray compartment.Thereupon, the lifter pad remains in its raised position as the camassembly completes the final portion of its revolution during which iteffects the tray indexing function performed when the projector isadjusted to its forward mode of operation.

GATE OPENING MECHANISM As the lifter pad moves downwardly to load aslide into the corresponding slide gate, that gate must be opened byretracting its fingers 207 in order that the slide can fall freely intoprojection position solely by virtue of gravity. Concurrently, theopposite slide gate obviously must remain in closed condition to avoiddisturbing the projected image of the slide in that gate. Thesefunctions are performed by the previously mentioned gate opening lever214 as best seen in FIG. 18 which is pivotally supported to the bottomplate 79 of carriage 76 by pivot stud 234 and therefore moves with thecarriage so that its nose portion 213 is engageable with the pressuremember tongue 211 of the slide gate in which a slide is to be replaced.The end of gate opening lever 214 opposite its nose portion 213 isprovided with a cam follower nose 235 positioned adjacent the peripheryof gate opening cam 236 at the bottom of lower cam member 86. Betweenslide changing operations, the gate opening lever 214 is free to moveslightly out of contact with the adjacent pressure member tongue 211 andtherefor has no influence on the pressure with which the correspondingslide is engaged by fingers 207. AS the cam assembly rotates, however,lobe 237 of cam 236 engages and displaces cam follower nose 235 of lever214 so that its opposite nose portion 213 presses against the adjacentpressure member tongue 211 to open the corresponding slide gate as shownin FIG. 15. This occurs just before the lifter arm 226 moves downwardlyin order that the slide can fall freely into place in the open gate.Thereupon, the continuing rotation of the cam assembly moves lobe 237beyond cam follower nose 235 so that the slide is resiliently engagedand held in proper projection position by the corresponding fingers 207.

After the mechanism carriage has shifted, nose 213 of lever 214 isaligned with the pressure member tongue 211 of the other slide gate,from which the previously displayed slide is returned to its traycompartment by upward movement of lifter arm 226. As that slidecommences its upward movement, the corresponding fingers 207 continue tohold it against the adjacent front wall surfaces of the slide gatestructure so that the slide is guided into the slide tray compartmentdirectly above disc notches 64. Before the slide has been liftedentirely into the slide tray, however, cam lobe 238 of cam 236 displaceslever 214 in the

1. A slide projector adapted to be loaded with a slide tray providedwith a row of slide compartments in which respective slides are carriedin a predetermined projection sequence, said projector comprising: twoslide gates in which individual slides may be received; means forselectively projecting an image of a slide received in one of said gatesand an image of a slide received in the other of said gates; means formounting and for shifting a slide tray loaded onto said projeCtor toalign said row of slide compartments thereof alternately with one ofsaid slide gates and with the other of said slide gates; means forindexing the slide tray loaded on to said projector to align differentones of said slide compartments thereof with the one of said slide gatesaligned with said row of slide compartments; and means for transferringsaid slides in said projection sequence from their respective slidecompartments into reception by alternate ones of said slide gates andfor returning each such slide from its slide gate to the respectiveslide compartment which it previously occupied in said tray after animage of that particular slide has been projected by said projectionmeans.
 2. The invention according to claim 1 wherein said tray shiftingmeans comprises cam means for imparting reciprocal movement to saidslide tray.
 3. A slide projector adapted to be loaded with a rotaryslide tray provided with a circular row of radially disposed slidecompartments in which respective slides are carried in a predeterminedprojection sequence, said projector comprising: two slide gates in whichindividual slides may be received; means for selectively projecting animage of a slide received in one of said slide gates and an image of aslide received in the other of said gates; means for mounting and forshifting a rotary slide tray loaded onto said projector to align saidcircular row of slide compartments thereof alternately with one of saidslide gates and with the other of said slide gates; means forrotationally indexing the slide tray loaded onto said projector to aligndifferent ones of said slide compartments thereof with the one of saidslide gates aligned with said row of slide compartments; and means foreffecting the transfer of a slide between its respective slidecompartment of said rotary slide tray loaded onto said projector and theslide gate with which that particular slide compartment is then aligned.4. The invention defined by claim 3 including actuating means fordriving and coordinating the operation of said projection means, saidtray shifting means, said tray indexing means and said slide transfermeans such that successive ones of said slides are thereby transferredout of their respective slide compartments in said slide tray loadedonto said projector and into alternate ones of said slide gates in saidpredetermined projection sequence and are thereafter returnedautomatically to their same respective slide compartments after imagesof those slides have been projected in said predetermined projectionsequence by said projection means.
 5. The invention defined by claim 4in which said actuating means includes a plurality of cam membersadapted to rotate in unison and a plurality of cam follower membersoperatively connecting respective ones of said cam members with saidprojection means, said tray shifting means, said tray indexing means andsaid slide transfer means to effect coordinated operation of those meansin response to rotation of said cam members.
 6. The invention defined byclaim 3 in which said projector is adapted to support said slide trayhorizontally above said slide gates, and to transfer slides verticallybetween said slide tray and said slide gates.
 7. A projector accordingto claim 3 adapted to be loaded with a slide tray including a discmember for retaining slides in their respective compartments in saidslide tray, said disc member including an opening with which differentones of said slide compartments can be aligned to allow a slide to bemoved to and from the particular slide compartment with which saidopening is aligned, said projector including disc orienting meansengageable with said disc member of said slide tray loaded onto saidprojector to locate said opening therein in alignment with the one ofsaid slide gates with which said circular row of slide compartments isthen aligned.
 8. A slide projector according to claim 7 in which saidprojection meanS includes lap dissolve means for gradually decreasingthe intensity of the projected image of a slide received in one of saidslide gates as the projected image of a slide received in the other ofsaid slide gates gradually increases in intensity, thereby providinguninterrupted transition between the projected images of successiveslides received in alternate ones of said slide gates.
 9. In a slideprojector including: two slide gates in which individual slides may beaccommodated; two projection lens assemblies located respectively inoptical alignment with corresponding ones of said slide gates to projectimages of respective slides accommodated thereby; lens support meanssupporting said lens assemblies for independent focus adjustingmovement; and image alternating means for alternating the projection ofsuch images between one of said lens assemblies and the other of saidlens assemblies; the improvement comprising: lens focusing meansselectively connectable with either of said lens assemblies to effectfocus adjusting movement of the particular lens assembly with which saidlens focusing means is so connected; focus adjustment selector meansoperable to connect said lens focusing means automatically with the oneof said lens assemblies that is projecting an image of a slide; a slidetray provided with a row of aligned slide compartments in whichrespective slides are carried in projection sequence; means for shiftinga slide tray loaded onto said projector to align said row of slidecompartments thereof alternately with one of said slide gates and withthe other of said slide gates; and means carried by said slide trayshifting means for operating said focus adjustment selector means. 10.The invention according to claim 9 wherein said slide tray shiftingmeans comprises a carriage for supporting said slide tray member, saidfocus adjustment selector means comprises a switch for selectivelyconnecting said lens focusing means to one of said lens assemblies, andsaid means for operating said focus adjustment selector means comprisesat least one projection carried by said carriage.